setting Auto-Submitted for notification mails

uses method from nextcloud/server#35876 if it exists, falling back
setting it via the swift message

Signed-off-by: Bennet Becker <dev@bennet.cc>

lib/MailQueueHandler.php

@@ -34,7 +34,7 @@
 use OCP\IURLGenerator;
 use OCP\IUser;
 use OCP\IUserManager;
-use OCP\L10N\IFactory;
+use OCP\L10N\IFactory; 
 use OCP\Mail\IMailer;
 use OCP\RichObjectStrings\InvalidObjectExeption;
 use OCP\RichObjectStrings\IValidator;
@@ -375,6 +375,12 @@ protected function sendEmailToUser($userName, $email, $lang, $timezone, $maxTime
 		$message->useTemplate($template);
 		$message->setFrom([$this->getSenderData('email') => $this->getSenderData('name')]);
 
+		if(method_exists($message, 'setAutoSubmitted')){
+			$message->setAutoSubmitted(\OCP\Mail\AutoSubmittedValue::AUTO_GENERATED);
+		} else {
+			$message->getSwiftMessage()->getHeaders()->addTextHeader('Auto-Submitted', 'auto-generated');
+		}
+
 		try {
 			$this->mailer->send($message);
 		} catch (\Exception $e) {